Hi Retyred - welcome to the forum!
Of the current cars, the only ones that come already converted to digital from the factory are the ones in the ARC Pro sets. Otherwise, it's a case of adding a C8515 digital plug to DPR cars (or C8516 for F1 DPR cars) or soldering in the C7005 Retro-fit chip to non-DPR cars.
Having said that, a few retailers do sell cars already fitted with a chip (usually the C8515 or C8516) for a price slightly less than the combined cost of DPR car + chip. One retailer I have used that does this is Jadlam Toys & Models. They also sell the cars from the digital sets.
When I was building up my digital fleet, I would look out for discount codes and sales and stock up on chips. £16 is the RRP, but I've rarely paid more than £13. However, I avoid buying used chips or older chips from auction sites - the latest versions are best. I do also move the digital plugs around my cars - not all are chipped all the time, just the ones I am racing. It helps keep the cost down a little.
I hope that helps.